Another LT4 blower on a LT1 620/672
 

I decided i'd like a winter project so in November I started to do this upgrade and I gotta say it wasn't that bad. If I had to piece the entire thing together it would have taken much longer but getting the kit from West Michigan Automotive Technology made it extremely simple and the entire installation took roughly 5-6 weeks working on it after work. Most of the time was spent waiting on tools to come in the mail such at torque wrenches and balancer pullers/installers. The worst part about it all IMO was getting the steering rack down and breaking tq on the crank bolt. I broke 2 big breaker bars during that process and at the ent of the day a 14" SK breaker bar and a cheater pipe took the win. The car started fine on the stock tune and did have a few lights mostly for map/baro. Along with the supercharger I added the LT4 Injectors, HPFP and 5% OD pulley. The addition of the extra coolant reservoir made servicing and bleeding the coolant extremely easy(installed but not hooked up in the pic). Otherwise everything else is completely stock. I don't plan on doing much more to the engine except for a trunnion upgrade and methanol. I did make a youtube channel which sorta goes over the process but ill warn you, its amateur footage and may not be very entertaining to watch.

The final numbers ended up being 620hp and 672 ftlbs on a mainline dynolog hub dyno. If anyone is in the Nashville area and looking for a good tune David at DBR High Performance did mine and I am extremely satisfied with it.

The car is amazing to drive now with power all over the place. I have to be careful while pulling out in traffic now since it is now quick to get away from you.

Anyways, I hope the Z06 guys keep on going bigger so those with the lt1's who want the oem look can too!

Thanks for looking!

https://www.youtube.com/channel/UC2p...SEfIQIwdVTsuaw

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added wiring harness relay and fuse mounting
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Varimax Pump
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Oem coolant reservoir
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Edelbrock additional reservoir
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Stand off for securing the wiring harness since it won't mount with the new brackets.

Nice job!

I've never seen a dyno like that, it's pretty cool and I bet much safer too!

It was so nice not worrying about tires.

I plan on putting on the 17 and up style on after getting everything else done. Maybe by then there will be more in circulation and not as expensive as they are today.

Congrats on the gains car looks fantastic
I also have LT1-LT4 headers and intake
was there a reason you went 5% OD pulley? and also you got the LT4 injectors what else did you got for the Fuel support?
thanks.

I went 5% OD because it would create more boost Im right around 9.5psi and didn't add any additional cost to the kit. For the fuel systems its just lt4 injectors and high pressure fuel pump.

Can you also post your torque curve? Did you have a video of the dyno? I am missing the dyno setup from your pictures.

I don't have any videos or pics of the dyno or video as I wasn't there when it was done. The Dyno is a Mainline Hub dyno

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Now it makes more sense. It’s really about 630tq/620hp. Which is awesome...and more inline with what I was expecting. I figured 7psi for 550-560whp. 8psi should be 570-580whp a s 9psi 600-610whp...I would expect torque to be a very similar number to HP.

Any idea what the stock psi is on the Z06?

No. It will be less that an LT1 with the stock Z06 pulley...because they have lower compression.

Mind educating me on how an engines compression ratio has an effect on a supercharger's boost level?

Boost is just the amount of pressure created...So, higher compression will result in higher boost with same pulley size...more pressure.

You will also see that things to reduce pressure, like adding a cam and headers will reduce boost with the same pulley size. So, I ran 8psi with stock cam...@575whp. I added a cam/headers and went to a smaller pulley size to run 8psi @715whp.

The pulley I needed to produce 8psi changed because I changed the way the engine would create pressure.

Hope this helps.

Uh, not quite. Your statement on reducing the indicated boost pressure (which is a factor of flow, and resistance to that flow) is correct - a higher overlap cam, headers, higher flow instake - will reduce "boost" as a result of more air flow at the same pulley size. Air pump efficiency.

But your compression ratio will not affect your indicated boost pressure in a measurable way on this type of compressor. Your compression ratio is one factor, your dynamic compression ratio is another factor. It is a separate column of pivots than changing the intake or exhaust flow to get a different indicated boost pressure.

Are you saying it is the intake exhaust differences between the Lt1 can and the Lt4 cam that causes the LT1 to see more boost/power with the same pulley size?

Indicated boost is a function of air flow. I can raise boost by lowering the efficiency of an engine intake or exhaust system depending on how I am adding the boost, and I may not get more power at all.

Boost does not equal power.

You said: Higher compression may result in more power (compression is how much air the cylinder takes in by swept volume by how much it compresses it at TDC). But static compression will not directly affect your boost pressure in a measurable way. What you do to affect you DYNAMIC compression (cam overlap, mainly) could.

Yeah I see what you are trying to say.

There is no doubt that when we compare the LT1 and the LT4, at the same levels of boost, the LT1 will produce more power when they both run the same pulley. The cam profile is different and so is the compression ratio.

I know I had the stock motor running 8psi and ran about 600whp. I made the motor more efficient and at 8psi I was running 715whp. I never intended to suggest that 1psi is equivalent to 1psi across different motors with different efficiency. However, for sure, when you are talking about a single motor, PSI does very easily translate into power.

There is also no question that when I took my motor and went from 8psi to 10psi to 12psi to 14psi power went up by about 30whp per pound of additional boost. I understand what you are trying to say, but for sure the smaller pulley pushes more air (results in more boost) and results in more power. It is very predictable.

We also took a motor and installed lower compression drop in pistons and with the same pulley, we saw less boost and less power. The only change was compression ratio in that situation. I'd have to go see if I still have logs from the runs after the pistons were installed to see exactly how much boost dropped. I thought it was about 1psi (which is significant if you are talking about a car that is only running 8-10psi).

I am a scientist and I will agree that my testing wasn't precise enough so I will trust what you are saying is correct...

Agreed that with the system staying static (your engine) and you increase input airflow, the boost (which we can think of resistance to flow), will indeed go up.

Boost is not a direct pivot. If you are stating that you made one change the system (compression ratio) and saw less boost, I would be intrigued to find out what the change was to the things that represent boost (volume of air, resistance to that mass air flow, etc).

The change is so small between large compression deltas...

Nice job! Did this on my Z51 and still adding a few things (got a ported 103 mm ported SC) looking at bigger throttle body (looking at a LT5 98mm) to match and upgraded cold air intake (may have to retune). I added the mighty mouse catch can to rid of the crap going back in the blower and installed an expansion tank, so no issues with heat soak but I am not a track rat. Agree about hi way driving, this baby will pull fast - I love it!